mailx cannot send special characters in subject

Good morning,

I'm trying to send email by using mailx, but three scenarios arise:

Scenario 1----------I send an email including US-ASCII chars only ( no special chars ) in its body message, but including them ( special chars ) in the subject - In this case the body msg is well interpreted, but the subject appears scrambbled

Scenario 2----------I send an email including special chars only ( no special chars ) in its body message, but not in the subject - In this case everything is correct.

Command:

echo "áéíóú" | mailx -s "aeiou" email_address

Results:

Content: (correct) - áéíóúSubject: (correct) - aeiou

Scenario 3----------I send an email including special chars in its body message, and subject - In this case, everything correct.

Command:

echo "áéíóú" | mailx -s "áéíóú" email_address

Results:

Content: (correct) - áéíóúSubject: (correct) - áéíóú

Summary:--------When the body messages has any special character, the subject is well interpreted when including special chars on it, but it's not when the body message doesn't have it, and subject does.

Current settings:-----------------LANG=es_MX.iso88591LC_CTYPE="es_MX.iso88591"LC_COLLATE="es_MX.iso88591"LC_MONETARY="es_MX.iso88591"LC_NUMERIC="es_MX.iso88591"LC_TIME="es_MX.iso88591"LC_MESSAGES="es_MX.iso88591"LC_ALL=